The present application claims the benefit of foreign priority upon German patent application 100 00 052.5, filed Jan. 3, 2000
1. Field of the Invention
The invention relates to an apparatus for producing and closing packs with multi-layered folding flaps by heat sealing with the aid of heated sealing jaws, in particular for closing (sheet-material) bags with closing flaps. The invention also relates to a mechanism for cyclically actuating sealing elements or similar tools.
2. Description of Related Art
The operation of sealing thermoplastic sheet materials poses difficulties if the surfaces which are to be sealed are of non-uniform thicknesses. This applies to folding flaps or closing flaps of packs or bags which on account of folds, in sub-regions, are of multi-layered construction.
The object of the invention is to propose an apparatus which is intended for sealing folding flaps, closing flaps or the like and is suitable, in particular, for compensating for regions of the folding or closing flaps which are of different thicknesses such that a uniform sealing surface or sealing seam is provided despite these differences in thickness.
In order to achieve this object, the apparatus according to the invention is characterized by the following features:
a) the packs or bags can be conveyed cyclically through a sealing station with a plurality of successive units comprising a heated sealing jaw, on the one hand, and (non-heated) mating jaw, on the other hand, between which the folding or closing flaps are accommodated for sealing purposes,
b) from unit to unit, the sealing jaws and mating jaws are positioned on alternate sides of folding or closing flaps such that in the region of one unit the sealing jaws are positioned on one side, and in the region of the next unit the sealing jaws are positioned on the opposite side, of the folding or closing flaps.
Favourable sealing results are achieved, in particular, with multi-layered sheet materials or flaps by successive sealing on opposite sides of the sheet material. Particularly precise sealing regions are achieved if, according to the invention, at least the (non-heated) mating jaw has an elastic abutment surface, for example comprising a silicone strip. In this case, that region of the sheet material or of the folding or closing flap which is to be sealed is forced against the elastic region of the mating jaw by the sealing jaw.
A special feature of the invention is a mechanism for actuating the sealing jaw or other elements which can be moved cyclically or back and forth. The mechanism is characterized by the following features:
a) a drive element which is driven continuously in rotation is connected, via a coupling member, to the element or the sealing or mating jaw,
b) the coupling member is connected pivotably to the element, on the one hand, and to an intermediate element, on the other hand,
c) the intermediate element can be moved by the drive element such that the driven element has a standstill phase during a revolution of the drive element.
The special feature of this mechanism is that entire cam plates which are susceptible to malfunctioning and/or provided with special lubrication and are intended for controlling the movement of the sealing jaws or the like are avoided. The crank-like mechanism, which, on account of the special connection to an actuating arm, ensures a standstill phase as rotation proceeds continuously, is of straightforward construction and is not particularly susceptible to malfunctioning.